Garton Ash's rebuttal is here. Key excerpt:

The pity of all this is that there is a vital debate to be had here - one on which the future of free societies in Europe will depend. The truth, apparent to those of us who live in the reality-based community, is that neither the extreme version of live-and-let-die separatist multiculturalism that Ali saw and rightly criticised in Holland (and that has also been seen in some British cities) nor the secularist republican monoculturalism preached by Bruckner and (partly) practised in France have succeeded in enabling Muslim immigrants and their descendants to feel at home in Europe - let alone, to identify themselves as European citizens. Nor has the German, Spanish or Italian way. The serious debate is about which elements from each approach can best be combined to make that happen. And what else can we do in that direction, for example by telling a new European story - one about Europeans coming from very different pasts but heading towards a shared future based on common goals.

This debate has only just started.